Having looked at the trial immigration rules in more detail, there are several notable omissions in the rules. It is noteworthy that the rules distinguish between having a valid PRC or DCPR issued in the past 10 years and merely having permanent residence. Although a DCPR is supposed to be valid indefinitely, the rules treat them as being valid for only 10 years. A valid PRC or DCPR qualifies one for indefinite leave to remain under Appendix EU. (It should become superior to other forms of ILR, which is why EU citizens will be able to upgrade from ordinary ILR to ILR under Appendix EU.)
Four categories of holders of permanent residence should apply for a DCPR or PRC if they do not have one that will be valid for a few years to come.
1. EU citizens whose EU citizenship may (effectively) expire in the next few years. Danish citizenship can expire, and once the UK has left the EU, I believe some Dutchmen resident in the UK could lose their Dutch citizenship. (The latter loss might take 10 years to start - I don't know the details.)
2. Non-EU nationals holding PR dependent on their formerly retaining a right of residence as a former extended family member or former family member other than a spouse when they ceased to be a family member because of a divorce. While one can argue that EEA Regulation 10(5)
is to be read as including stepchildren etc. of the EEA national, I don't see how one can extend that reading to sub-paragraph (d) of the definition of a "family member who has retained the right of residence" in the forthcoming Appendix EU. Granting leave to remain to those who had a retained right of residence is a concession,* not a proposed treaty obligation.
3. Non-EU beneficiaries of Surinder Singh. Many will fall foul of EEA Regulation 9(4)
. Regulation 9(4)(a) excludes those who deliberately set about obtaining Surinder Singh rights; Regulation 9(4)(b) excludes any who obtained the right as extended family members. I suggest it may be prudent to challenge the regulations while the UK is still issuing PRCs. While Regulation 9(4)(a) and probably also Regulation 9(4)(b) are contrary to EU law, granting leave to remain to beneficiaries of Surinder Singh is also a concession.*
4. Non-EU EEA citizens. After careful reading, I have concluded that, for example, a former family member of a 'qualifying British citizen' can also qualify for leave under new Rule EU11. Thus, I see nothing to stop a Norwegian qualifying for ILR by virtue of his DCPR, even though, so far as I am aware, no relevant deal has yet been provisionally agreed with Norway.
*I believe it will be a treaty obligation in at least some case where the current right holder is also the family member of an EU national, e.g. by marrying an EU national who retains his old treaty rights.